Highlights on the Role of Fe, Sr, and Solidification Time on Porosity Formation in Al–Si Cast Alloys

Abstract

The present study was undertaken to elaborate on the parameters controlling the microstructural characterization of A319.2 Al–Si alloys, as a function of iron content (0.12–0.8%), Sr addition (~250 ppm), and solidification time (586s vs 513s). For comparison, selected conditions were applied to A356.2 alloys. The use of a hot graphite mold and an end-chill mold provided different solidification rates along the liquid/solid interface, corresponding to DAS values in the range of ~23–85μm, corresponding to levels of 5, 10, 30, 50, and 100 mm above the chill end. Addition of strontium leads to fragmentation of β–Al₅FeSi platelets. Under similar Fe level and solidification rate conditions, the A319.2 alloys exhibit larger pore sizes than the A356.2 alloys, due to the absence of the (Al–Al₂Cu) reaction in the latter and hence longer solidification time. Four types of iron intermetallics were reported viz., δ-, α-, β-, and π-phases.